Real Time Probing of Self-Assembling Process Steps in InAs/GaAs Quantum Dot Growth

Self-assembling process of InAs/GaAs quantum dots (QDs) has been investigated by analyzing reflection high-energy electron diffraction (RHEED) images. During the island formation, the chevron diffraction of the RHEED shows dramatic changes depending on the As pressure. The self-assembling process has been found to consist of four steps. Initially islands are preferentially covered by high-index facets, which transform into low-index surfaces as the growth proceeds, and then the islands are covered by stable low-index facets. In this growth step, the island size becomes uniform, because of the self-limited growth. In the next step, we found indium flow back from the islands into the wetting layer, which causes shrinkage of the island size as well as formation of giant islands. This indium flow back can be controlled by As pressure.